I'm interested in making a cooler and a saddle cover in particular, and possibly other things as well. Does anyone have patterns they can share? Or advice? I'm not the greatest DIY person... but I really need to save money!
Try Suitability patterns. I've used the horse blanket one; the hay bags pattern; the nose bag and the cantle bag. Oh, and the saddle cover and bit carrier. They were pretty easy to follow, although I've been sewing for 40+ years, so can't really say what they might be like for a beginner (sorry if you're not; kind of assumed that from your post).
The hardest part was trying to draw the horse blanket on the fabric. After making a couple, I laid down a ready-made blanket that I knew fit and traced that. Also, if you make the saddle carrier, the quilting step is a pain--lots of stuff to fit in the sewing maching.
That said, good luck. It's fun to do your own because you can use the color you want.